Plastic composition



' June 25, 1946 PLASTIC COMPOSITION Isador J. Novak, Trumbull, Conn, and Joseph N.

Kuzmiok, Passaic, N. 1., assignors to Raybestos- Manhattan, Ina, Pascale, N. J., a corporation of New Jersey No Drawing. Application March 8, 1943, Serial No. 418,419

13 Claims.

This invention relates to the production of a plastic composition having rubber-like properties, and more particularly to a combination of a vinyl resin and a non-volatile, vulcanizable plasticizer and the vulcanization treatment of the combination to reduce the thermoplasticity thereof or to form products having a minimum of heat sensitivity.

More specifically our invention relates to the combination of a polyvinyl acetal resin and am!- canizable vegetable or fish oil soluble therein and to the vulcanization of the oil component of the composition with preferred vulcanizing agents, the composition being amenable to mixing, milling, molding, vcalendaring, frlctioning and extruding similar to normal rubber compounds, and to the production of materials which are stable to change on aging, resistant to a wide range of temperature varlation,'resistant to paramnic solvents, oils and ozone, of good electrical properties, and good tensile strength and appreciable elongation characteristic, among other advantages.

It is recognized that vinyl compounds or poly vinyl resins have been plasticized with many organic esters, alcohols and the like. Such resulting mixtures or solutions are characterized in general by their toughness, flexibility and elasticity at room temperature, these properties, of course, being modified by the selection and proportion of the constituents. One serious fault,

however, has been their sensltiveness to heat.

Depending on the amount of plasticizer, such compositions lose strength and resistance tofiow at temperatures of from 120 to 200 F. and may actually melt at 300 F. Also their cold resistance is relatively poor, much below 32 F., the composition freezing and becoming brittle. Such sensitivity to temperature has precluded their use in many places where rubber or chloroprene are used. For example, resistance to heat -is necessary in steam packing compositions, ignition wire insulations, steam and hot water hose, and mechanical rubber articles exposed to variations in temperature.

It is likewise well known that oils such as linseed, soyabean, cottonseed, corn and the like, which are normally liquid, can be set or solidified by the action of heat-and reagents such as sulphur chloride, benzoyl, peroxide, boron fluoride, etc., to form materials which while stable to temperature change and are resilient, have poor elasticity and are short or weak to a shearing force.

The present invention relates to the combination of oils ofthe foregoing class and like drying, semi-drying, or non-drying oils, preferably in the blown forms, as he *uinafter more fully set forth, and which have considerable absolute ethyl alcohol solubility and are compatible with the polyvinyl acetal resins, and which can be vulcanized in association, distribution or solution therewith by means of oxidizing vulcanizers to form products of greatly reduced thermoplasticity and of increased cold resistance.

The polyvinyl acetals made use of by us in accordance with the present invention are a family or resins made from polyvinyl acetate by the successive or combined steps of hydrolysis and condensation with aldehydes. Thus for example, polyvinyl acetate is hydrolyzed to yield polyvinyl alcohol, and the polyvinyl alcohol is caused to react with an aldehyde such as butyr aldehyde to form polyvinyl butyral. Similarly the use of 9. formaldehyde or acetaldehyde results respectively in the corresponding formal or ace tal, the resins being recovered and used in the form oi granular preciptiates.

As previously indicated, the oils used by us in combination with the polyvinyl acetals and as plasticizers therefor are vulcanizable vegetable or fishoils of the factlce forming type having considerable absolute ethyl alcohol solubility and compatibility with those resins, at least in and preferably in the blown state. Thus although we may use such oils as linseed, soyabean, cottonseed, corn, perilla, menhaden, pilchard, oiticlca, hempseed and the like in either the blown or unblown state, others such as castor and China designated which are capable of being vulcanized as herein set forth, in either the unblown or fluid blown state, or the blown state alone.

In order to obtain the maximum of the foregoing desirable properties of alcohol solubility and compatibility we have found that the most satisfactory form of oil is one which has been air or oxygen blown to an extent where it has a viscosity of from about 2 to about 100 poises, and preferably in the range of from about 10 to about 20 poises at normal room temperature or about 72 F. This blowing is preferably conducted at a relatively low treatment temperature such as from about to about F., although .the blowing may be conducted at temperatures preferable since there is more conversion and less break-down product present- It will also be understood that each of these oils and the resins are not necessarily equivalent in the character of the'result produced, and that varying proportions to accomplish related results may be required. Also the conditions of compounding may likewise be dependent on the particular oils, resins and other compounding materials and the specific use of the resultant product.

In accordance with the present invention we have found that oxidizing type vulcanizing agents effectively serve to vulcanize the aforesaid compatible factice forming type of vegetable oils while in intimate plasticized association with the polyvinyl acetal resin. Thus we are able to form mixed compounds of these resins and oils wherein at least the oil component can be vulcanized and the mixture due to the aforesaid association caused to be thereby thermosetting. Among such suitable vulcanlzing agents may be mentioned lead peroxide, benzoyl peroxide, chromic oxide and the like compositions from which oxygen is evolved at vulcanization temperatures, such as for example, 240 to 310 F. In association with these vulcanizing agents we may use suitable accelerators such as paraquinone dioxime and the like rubber vulcanization accelerators.

In compounds of the aforesaid resins and oils, the oils not only act as composition or product modifying materials but as plasticizers for the nature of the ultimate product desired we may incorporate from about to about 200 and preferably about to about 100 parts by weight of the oils to 100 parts by weight of the resins.

with the lower proportion of oil tensile strength of 2500 pounds per square inch with 150% elongation can be obtained. The addition of our oils also increases the freeze resistance of the vulcanizate so that it is possible to formulate mixes capable of flexibility at 50 F., in addition to being stable at temperatures of 200 to 300 F. for long periods without marked change.

Methods of incorportting the vulcanizable oil and the polyvinyl acetal resin may. vary widely depending onthe nature and condition of the resin and the characteristic solubility or compatibility of the resin with the oil. Thus for example the dry resin powder may be mixed by wetting it with the oil, allowed to stand for a short time and then thoroughly combined in an internal type mixer or on a rubber mill at a temperature of from about 200 to about 300 F'., depending on the softening point of the resin.

On the other hand it is generally more convenient to first employa coupling solvent or plasticizer which induces compatibility at lower temperatures and produces a uniform single phase mixture. These coupling solvents may be of the volatile or non-volatile type, but should .not be of a type or in such proportion as to prevent the combination from vulcanizing. These coupling solvents may be of the organic ester, ether or acetone type and specifically such materials as "Flexol-3GH (triethylene glycol di-2- ethylbutyrate), methyl ethyl ketone, isopropyl alcohol, dibutyl sebacate, phthalate, etc., have been found satisfactory.

As an example of a typical compound having good properties and the procedural composition steps, 100 parts by weight of polyvinyl butyral resin in the unplasticized granular form, 100 parts by weight of 10 to 20 poise at 72 F. low temperature blown linseed oil, and 20 parts by weight of Flexol-3GH may be thoroughly mixed in a dough or any other appropriate type of mixer to provide a loose mixed mass of oily granules. This mass may then be seasoned in a warm atmosphere to permit good diffusion of the plasticizers in, the resinto convert it into. a rubbery plastic mass which can then be put on a hot rubber mill or in a Banbury mixer for mastication. In this mastication step further compounding may be carried out by addition of fillers as in the compounding of rubber such as channel black, together with addition of the vulcanizing agent, which may be 5 parts by weight of chromic oxide.

The resulting compound has the general physical appearance of milled uncured rubber and may then be handled and vulcanized in a manner similar to rubber compounds and similarly molded, extruded, frictioned and calendered. Thus the compound may be formed in molds and a *5 inch slab cured in 20 to 30 minutes at a temperature of about 290 F. to 310 F. 'Asan indication of the degree of vulcanization, cured material can be stripped from the hot mold at 300 F. with a permanent set, which of course is not possible with a thermoplastic material, as the latter even if molded hot, must be cooled before removing from the mold. vulcanization may also be accompiished in open steam or hot water. Hot air cures can also be made on coated or spread cloth, the composition for spreading having first been made into a dough with a, solution such as a blend of 20% isopropyl alcohol and of an aromatic such as toluol, xylol, etc., the spread composition being curable at temperatures as low as 250 F. for A to 1 hour.

Compound No.

Polyvinyl butyral resin 100 100 Fluid low temperature blown linseed oil 20 100 Fluid low temperature blown castor oil. 50 Flexol-3GH 20 Dibutyl sebacate 20 Channel black. 25 42 55 Stearic acid 2 2 2 Lead peroxide... l0 Benzoyl peroxide 5 Cbromic oxide 5 Paraqnlnone dioxeme 2 2 (HIRED 20 MINUTES AT 310 F.

Tensile strengtb lbs. per sq. in 2, 200 2, 100 l, 000 Elongation, per cent 200 lilo Durometer hardness 82 73 do 7 DAYS AGING IN GEER OVEN AT 153 F.

Tensile strength, lbs. per sq. in s 3, 400 3, 200 l, 500 Elongation, per cent 78 I10 I00 Duromctcr hardness. Q9 93 34 Cold test 96 hours at 0 F Cold (at 96 hours at -50 F F) Per cent swelling in M-zzz aviation gm, 96

hours at room temperature 4. 0 l2 0 H. 0

Flexible. Brittle.

anoaen of 200 to 300 F. for long periods of time without marked change and being characterized by toughness, flexibility and elasticity over a wide range of conditions, and remaining flexible at temperatures ranging down to 50 F. In addition its excellent resistance to parafflnic solvents and oils, other than aromatic solvents puts it in a class with such synthetics as Neoprene and the like, and may be used for-many purposes where rubber is now used.

Suitable uses oi our compositionshave been found in steam packing compositions. ignition wire insulations, steam and hot water hose, mechanical rubber articles exposed to variations in temperature, raincoats, hospital sheeting, and many other articles and uses.

We claim as our invention:

1. The method oi forming a heat stable and cold resistant rubber-like plastic composition which comprises combining and plasticizing a polyvinyl acetal resin with from about 20% to about 200% by weight thereof of a factice producing glyceride oil, and curing said composition at a temperature of from about 240 F., to. about 310 R, for a period of from about twenty to about sixty minutes in the presence of a vulcanizing agent adapted to liberate oxygen at said tem perature.

ture of from about 240 F., to about 310 F., in the presence of a vulcanizing agent adapted to liberate oxygen at said temperature.

6. The method of forming a heat stable and cold resistant rubber-like plastic composition 7 which comprises combining and plasticizing a to thermoset condition by heating at a temperapolyvinyl acetal resin with from about 20% to about200% by weight thereof of a compatible fluid blown ractice producing glyceride oil having a viscosity of from about 10 to about 20 poises at 72 F., and curing the cilia said composition ture of from about 240 F., to about 310 F., in the presence of a vulcanizing agent adapted to libera-te oxygen at said temperature.

7. A thermoset heat stable and cold resistant, tough, fllexible, elastic, rubber-like plastic composition comprising a p lyvinyl acetal resin in plasticized association with trom about 20% to about 200% by weight thereof of a compatible factice producing glycerideoil, produced by heat ing the resin and oil to a temperature of about 1 240 F., to about 310 F., in the presence of a 2. The method of forming a heat stable and cold resistant rubber-like plastic composition which comprises combining and plasticizing a polyvinyl acetal resin with from about 20% to about 200% by weight thereof of a compatible fluid blown iactice producing glyceride oil having appreciable ethyl alcohol solubility, and curing the oil in said composition to thermoset condition by heating the composition at a temperature oi from about 240 F., to about 310 F., in the presence of a vulcanizing agent adapted to liber-' polyvinyl acetal resin with from about 50% to about 100% by weight thereof of a factice producing glyceride oil and curing said composition to thermoset condition by heating at a temperature of from about 240 F., to about 310 F., in the presence of a vulcanizing agent adapted to liberate oxygen at said temperature.

5. The method of formin a heat stable and cold resistant rubber-like plastic composition which comprises combining and plasticizing a polyvinyl acetal resin with from about 20% to about 200% by weight thereof or a factice pro-,

ducing s yceride oil and curing said composition to thermoset condition by heating at a temperavuicanizing agent adapted to liberate oxygen at said temperature.

8. A thermoset heat stable and cold resistant, tough, flexible, elastic, rubber-like plastic composition comprising a polyvinyl, .acetal resin in plasticized association with from about 50% to about by weight thereof of a fluid blown compatible factice producing glyceride oil, produced by heating the resin and oil to a temperature of about 240 F., to about 310 F., in the presence of a vulcanizing agent adapted to liberate oxygenat said temperature.

9. A thermoset heat stable and cold resistant, tough, flexible, elastic, rubber-like plastic composition comprising polyvinyl acetal in plasticized association with from about 20% to about 200% by weight thereof of a fluid blown factice forming glyceride oil, produced by heating the resin and oil to a temperature of about 240 F., to about 310 F., in the presence of a vulcanizing agent adapted to liberate oxygen at said temperature.

10. A thermoset heat stable and cold resistant, tough, flexible, elastic, rubber-like plastic composition comprising polyvinyl butyral in plasticized association with from about 20% to about I 200% by weight thereof of a fluid blown factice forming glyceride oil, produced by heating the resin and oil to a temperature of about 240 F., to about 310 F., in the presence of a vulcanizing agent adapted to liberate oxygen at said tem- P rature.

11. A thermoset heat stable and cold resistant, tough, flexible, elastic, rubber-like plastic composition comprising a polyvinyl acetal resin in Dlasticiz'ed association with from about 20% toabout 200% by weight thereof of fluid blown linseed oil, produced by heating the resin and oih to a temperature of about 240 F., to about 310 F.,

in the presence of a vulcanizing agent adapted cold resistant rubber-like plastic composition which comprises combining and plasticizmg a polyvinyl acetal resin with from about 20% to about 200% by weight thereof of a factice producing glyceride 011, and curing'the oil in said composition to thermoset condition by heating the composition at a temperature of from about 240 F., to about 310 F.. in the presence of an organic peroxide adapted to liberate oxygen at said temperature.

IZADOR J. NOVAK. JOSEPH N. KUZMIC'K. 

